Increasing population and industrialization of the world's economies means the demand for fresh clean water for use has increased while the supply has decreased because of the increased pollution of many fresh water sources. In an attempt to overcome this, there has been the realization that a number of quite large polluted water sources need to be cleaned before the water can be either disposed to the environment or reused. The volumes of water and their pollutant loadings are such as to make filters unsuitable for all but the most lightly polluted water sources. Chemical dosing with large settling ponds is a possibility for smaller volumes of water, where reasonably sized ponds are acceptable to store the water over a few days. Chemical dosing adds to the salinity of the water and salinity of many water tables is already a significant problem. Using dissolved air flotation (DAF) systems is another possibility, but their costs are high and they require chemicals. Electrolytic water treatment systems offer the possibility to treat large volumes of water without the disadvantages of the other two systems.
Electroflocculation, one of the electrolytic water treatment techniques, involve the passage of an electric current between two electrodes, at least one of which is a metal that gives off flocculating ions, either Al+++ or Fe+++ when used as an anode. These metal ions adhere to pollutants in the water, flocculating them. Cathode reactions include the generation of H2 gas micro bubbles. If the system is arranged correctly, these gas micro bubbles capture the flocculated particles and float them up to the surface, from where they can be easily removed.
This process has been successfully employed for small volumes of water at rest in closed containers. In this technique, water is pumped into a container, treated, allowed to rest while the remaining pollutants and gas bubbles float to the surface and then pumped out. It is not suitable for large volumes of water because of the times to pump the water into the container and pump it out again. As the volumes get larger, the time to pump the water in and out of large containers makes the process less viable.
There are many situations where it is desired to treat large volumes of water per day. Some electrolysis based water treatment systems have been developed that can dose mega liters of water per day with metal ions. Most of these involve the use of filters to remove the pollutants after they have reacted with the metal ions. This poses serious problems if the water is heavily polluted or contains substances such as oil that can foul filters. Some involve the use of open containers with plates such that the water flows through and is flocculated. However there the objective is flocculating the pollutants, with pollutant removal still occurring by using filters or settling tanks. Still others use closed containers with the flocculated particles and bubbles in the water being carried through to the separation phase (either filters or settling). These all have a number of disadvantages as far as operating efficiency is concerned
These problems can be overcome in a system that enables the water to flow continuously while the pollutants are floated to the surface and removed. It is the objective of the apparatus described in this application to demonstrate a mechanism by which the bubbles generated by the electrolytic process can be used directly to capture the pollutant particles flocculated by the Al and/or Fe metal ions, float them to the surface where they remain, to be removed without the need for any additional foaming or floc capture chemicals, or using a filter to remove them. It should be noted that this process is scaleable in size and the same criterion can apply for small and large sized systems.